The soil in raised beds is easy to improve with additions of organic matter, and since it warms up faster than in-ground beds, you can plant sooner.

Preparing Garden Soil

Raised beds with lots of organic matter dug in provide "growing-only, no-walking" areas that encourage extensive, healthy root growth and allow better drainage. Here's how to get some started.

Adding Green Manure
If you grow green manure crops, cut the top growth and till or dig the plants into the soil. Wait about two weeks before transplanting vegetable and flower seeds or seedlings. This will allow the greenery to decay sufficiently to provide nutrients to the new plantings. The initial heat produced from the decomposing green manure will burn seeds trying to sprout or transplants trying to get settled in.

To loosen clay soil and provide slow release of nutrients, add up to 50 percent organic matter to the soil -- leafy material, straw, grass clippings, and non-greasy kitchen vegetable scraps. Sand will not do the job; remember that contractors mix sand and clay and water to make cement. Continue applying organic matter as mulch throughout the year. Turn it all under in the fall for a rich and friable soil in the spring.

Teach your plants to grow deeply for moisture. In spring, for average soils, water deeply only every two to three weeks. By the time summer's heat arrives, plant feeder roots will be growing deeply for moisture, and the plants won't need watering more frequently than once a week during very hot spells.

One inch of irrigated water will soak down to different depths, depending on how heavy your soil is: 12 inches deep in sandy soil, 9 inches deep in loamy soil, but only 3 inches deep in clay soil. Plant root zones generally reach from 2 to 12 inches down.
Because clay soil is so compact, it can be watered a little each day for two or three days to allow absorption down to the root zone. If you apply too much water at one time, much of it will runoff and be lost. Clay soil will retain this moisture for a much longer period than sandy soil, which is very porous. Soil with a lot of organic matter is the best because it holds lots of water but still allows air in for best plant root growth.

Determining Your Soil's Texture
To easily determine the texture of your soil, fill a jar two-thirds full of water, then add soil to the top. Shake the jar well and place it on a windowsill where you can observe the results without moving it. After a few days, the layers will be apparent, and you can make your analysis. The heavy sand particles will settle first to the bottom of the jar, followed by the silt and then the clay. Organic matter will float. Good loam contains about 45 percent sand, 35 percent silt, and 20 percent clay.

If you've been improving your soil and want to see how far you've come, take another sample from some unimproved soil nearby, and test it the same way.